The government warned this summer that the overuse of antibiotics was leading to the development of resistant bacteria, and warned that diseases such as tuberculosis could spread alarmingly unless the use of antibiotics was curtailed.

However, scientists from the University of Limerick have developed a technique that may help to combat the threat.

The Journal of Organic Chemistry reports that the scientists have altered the structure of penicillin to make it effective against antibiotic-resistant strains of bacteria.

In common with other antibiotics, penicillin's effectiveness as an antibiotic has diminished since its widespread introduction in the 1940s, due to the ability of various bacteria to develop resistance to the drug.

Some bacteria are able to negate penicillin's infection-fighting properties by producing enzymes that cut out a critical part of the penicillin molecule.

To counter this, the typical response is to combine the penicillin with a chemical substance that inhibits the action of the enzymes.

However, after a while, the bacteria develop additional resistance to the new substance and render the updated penicillin version ineffective.

Fatal to bacteria

Researchers could be close to a breakthrough

The Irish research team has produced a prototype penicillin structure that works by incorporating a unique fragment to the penicillin molecule, which is fatal to bacteria and specifically activated only when a bacterium attempts to change the drug's molecular structure.

Any bacterium that does not produce the relevant enzymes would still be killed off by the normal action of the intact penicillin.

Research leader Dr Timothy Smyth said: "There is some way to go yet to deliver a therapeutically useful drug.